Device and arrangement for producing a three-dimensional object

ABSTRACT

A device for manufacturing a three-dimensional product, which device comprises a work table on which said three-dimensional product is to be built, a powder dispenser which is arranged to lay down a thin layer of powder on the work table for the formation of a powder bed, a ray gun for giving off energy to the powder whereby fusion of the powder takes place, members for controlling of the beam released by the ray gun across said powder bed for the formation of a cross section of said three-dimensional product through fusion of parts of said powder bed, and a controlling computer in which information about successive cross sections of the three-dimensional product is stored, which cross sections build the three-dimensional product, the controlling computer intended to control said members for guiding the ray gun across the powder bed according to a running schedule forming a cross section of said three-dimensional body, whereby said three-dimensional product is formed by successive fusion of successively formed cross sections from powder layers successively laid down by the powder dispenser.

TECHNICAL FIELD

[0001] The invention relates to a device and a method for manufacturingof a three-dimensional product through successive fusion of chosen partsof powder layers, placed on a worktable.

TECHNICAL BACKGROUND

[0002] A device is previously known, e.g. through U.S. Pat. No4,863,538, for manufacturing of a three-dimensional product throughsuccessive fusion of chosen parts of powder layers, applied to aworktable. The device comprises a work table on which saidthree-dimensional product is to be formed, a powder dispenser, arrangedto lay down a thin layer of powder on the work table for the formationof a powder bed, a ray gun for delivering of energy to the powderwhereby fusion of the powder takes place, elements for control of theray given off by the ray gun over said powder bed for the formation of across section of said three-dimensional product through fusion of partsof said powder bed, and a controlling computer, in which information isstored concerning consecutive cross sections of the three-dimensionalproduct. The three-dimensional product is built up through fusion ofchosen parts of consecutively added layers of powder. The controllingcomputer is intended for the control of deflection elements for the raygenerated by the ray gun over the powder bed in accordance with arunning schedule, which depicts a predetermined pattern. When therunning schedule has fused the desired area of one powder layer, a crosssection of said three-dimensional body has been formed. Athree-dimensional product is formed through consecutive fusions ofconsecutively formed cross sections of powder layers, successively laiddown by the powder dispenser.

[0003] When a device according to the state of the art us utilized formanufacturing of three-dimensional products, it has become apparent thatdeviations from the desired shape, size, and strength arise.

SHORT DESCRIPTION OF THE INVENTION

[0004] One object of the invention is to provide a device for themanufacturing of three-dimensional bodies through successive fusion ofchosen parts of powder layers, laid down on a work table, in whichreduction of deviation from the desired form, size, and strength of athree-dimensional body is made possible.

[0005] This object is achieved through a device in accordance with thecharacterizing part of patent claims 1 and 25. By providing an elementfor the sensing of surface characteristics of a surface layer,positioned on the powder bed, measurement and correction of thecharacteristics of the surface are made possible, whereby a product withreduced deviation from desired dimensions and surface irregularity canbe achieved. In a preferred embodiment of the invention, the temperatureduring fusion of the powder particles is measured, whereby it ispossible to ascertain that the fusion takes place within a definedtemperature range, whereby the risk is reduced for appearance ofdefects, e.g., through vaporization or boiling of the material.Vaporization and boiling of the material may give rise to welding sparksor other surface irregularities. This element also allows measurement ofthe cooling temperature of specific fused parts in a powder layer,whereby the risk for appearance, and the size, of any surface tension inthe fused part may be reduced, thereby reducing unwanted changes inshape. Further, measurement of the dimensions of the cross section ismade possible, whereby a comparison of the dimensions of the formedcross section with the intended cross section of the object can be usedto calibrate the controlling elements of the ray gun. The element alsoallows measurement of the temperature of the unmelted powder bed,whereby maintenance of an advantageous temperature from the point ofview of the process can be monitored.

[0006] According to a preferred embodiment of the invention, informationon the temperature distribution in the surface layer of the powder bedis fed back to the control computer for adjustment of the runningschedule over the surface layer of the powder bed. Changing the runningschedule and the power and/or appearance of the beam enables a correcttemperature to be maintained in the different parts of the powder bed.

[0007] In a further preferred embodiment of the invention, theinformation concerning the temperature distribution in the surface layerof the powder bed is utilized to increase energy delivery within areasof the surface layer of the powder bed, in which the temperature is toolow, and to decrease the delivery of energy within areas in which thetemperature is too high, whereby a less fluctuating working temperaturein the cross sections is obtained. Through adaptation of the energydelivery to specific parts, a more correct temperature distribution isobtained, whereby the quality of the product can be improved.

[0008] In a further preferred embodiment of the invention, the device isarranged to control the energy delivery from the ray gun in areas fusedwithin the presently uppermost powder layer, in such a way that themaximum temperature after fusion in these areas is within a limitedrange. By controlling the energy delivery in such a way that too hightemperatures are avoided, the risk of boiling and vaporizing thematerial, with ensuing defects, can be reduced.

[0009] In yet a further embodiment of the invention, said information onthe temperature distribution is utilized to control energy delivery froma ray gun, which is part of the device, to the powder bed, in areaswhich are being fused within the presently uppermost powder layer, andwhich are to be united with areas within a subsequent layer, in such away that the minimum temperature in these areas does not fall below apredetermined limit. By ascertaining that the temperature does not fallbelow a predetermined limit, the risk for appearance of surface tension,with ensuing deformation of the product, can be reduced.

[0010] In yet another embodiment of the invention, said information onthe temperature distribution is utilized to control the energy deliveryfrom the ray gun to the powder bed in unfused areas within the surfacelayer of the powder bed, in such a way that the temperature within theseareas does not fall below a second predetermined limit. By maintaining acertain temperature in the powder bed not intended to be fused, thecooling process in areas already fused or to be fused can be controlledmore closely on the one hand, and on the other the disturbances arisingfrom transfer of the beam across areas not intended to be fused, inorder to reach different areas scheduled for fusion, can be reduced.

[0011] In a still further preferred embodiment, the surface irregularityis measured, preferably by a camera that registers shadow formation onthe surface, whereby the surface structure can be read. Uponregistration of occurrence of surface irregularities, e.g., arising froma welding spark or in some other way, the ray gun can be ordered to anidentified coordinate in order to melt down the identified irregularity.

[0012] In one preferred embodiment of the invention, the powder bed andthe ray gun are enclosed in a chamber, which is equipped with atransparent window, protected by a film, which is feedingly arrangedalong the window, whereby new film is being fed. By feeding the film asit is being coated, the transparency through the film and through thewindow can be maintained.

[0013] A second object of the invention is to provide a method for themanufacturing of three-dimensional bodies through successive fusion ofparts of a powder bed, which parts correspond to consecutive crosssections of the three-dimensional body, in which reduction of deviationfrom the desired form, size, and strength of a three-dimensional body ismade possible.

[0014] This object is achieved through a device in accordance with thecharacterizing pars of patent claims 15. By providing an element for thesensing of surface characteristics of a surface layer, positioned on thepowder bed, measurement and correction of the characteristics of thesurface are made possible, whereby a product with reduced deviation fromdesired dimensions and surface irregularity can be achieved. In onepreferred embodiment, the temperature distribution in a surface layer inthe powder bed is registered, which enables temperature control duringfusion of the powder particles. This makes it possible to ascertain thatthe melting takes place within a defined temperature range, whereby therisk for occurrence of defects, e.g., through boiling or vaporizing ofthe material, can be reduced. This element also allows measurement ofthe cooling temperature of specific fused parts in a powder layer,whereby the risk for appearance of any surface tension in the fused partmay be reduced, thereby reducing the risk for occurrence of unwantedchanges in shape. Further, measurement of the dimensions of the crosssection is mad possible, whereby a comparison of the dimensions of theformed cross section with the intended cross section of the object canbe used to calibrate the controlling elements of the ray gun. Theelement also allows measurement of the temperature of the unmeltedpowder bed, whereby maintenance of an advantageous temperature from thepoint of view of the process can be monitored.

[0015] In yet a preferred embodiment, the surface irregularity ismeasured, preferably by a camera that registers shadow formation on thesurface, whereby the surface structure can be read. Upon registration ofoccurrence of surface irregularities, e.g., arising from a welding sparkor in some other way, the ray gun can be ordered to an identifiedcoordinate in order to melt down the identified irregularity.

[0016] Further preferred embodiments are given in the enclosedsub-claims.

DESCRIPTION OF THE FIGURES

[0017] The invention will be further described below, in conjunctionwith the enclosed drawings, in which:

[0018]FIG. 1 shows a cross section of the invention,

[0019]FIG. 2 shows a side view of a chamber equipped with a transparentwindow,

[0020]FIG. 3 shows a device for feeding and fixing of a protective filmfor maintaining transparency of the window,

[0021]FIG. 4 shows a flow chart for the generation of primary runningschedules,

[0022]FIG. 5 shows a flow chart for a running schedule of the device,

[0023]FIG. 6 shows a flow chart for the correction of said runningschedule,

[0024]FIG. 7 shows the schematic build-up of a three-dimensional object,and

[0025]FIG. 8 shows a number of cross sections from FIG. 7.

EXAMPLES OF EMBODIMENTS

[0026] In FIG. 1, a device is shown for the manufacturing of athree-dimensional product, generally designated by 1. The devicecomprises a work table 2, upon which a three-dimensional product 3 is tobe built, one or more powder dispensers 4, and members 28 arranged tolay down a thin layer of powder on the work table 2 for the formation ofa powder bed 5, a ray gun 6 for releasing energy to the powder bedwhereby fusion of parts of the powder bed takes place, control members 7for the beam released by the ray gun 6 over said work table to form across-section of said three dimensional product through fusion of saidpowder, and a controlling computer 8 in which information is stored onsequential cross-sections of the three-dimensional product, whichcross-sections constitute the three-dimensional product. During a workcycle the table will be lowered successively in relation to the ray gunafter each added layer of powder. In order to make this movementpossible, the worktable is in one preferred embodiment of the inventionarranged movably in vertical direction, i.e., the direction indicated bythe arrow P. This means that the worktable starts in an initial position2′, in a position where a first powder layer of necessary thickness hasbeen laid down. In order not to damage the underlying worktable, and inorder to provide sufficient quality of this layer, it is made thickerthan the other applied layers, whereby melt-through of this first layeris avoided. The worktable is thereafter lowered in connection withlaying down a new powder layer for the formation of a new cross-sectionof the three-dimensional product. In one embodiment of the invention,the worktable is for this purpose supported by a scaffold 9, comprisingat least one rack 10, supplied with cogging 11. A step or servo engine12, equipped with a gear 13, positions the worktable in the desiredvertical position. Other devices for adjustment of the working height ofa worktable, known to those skilled in the art, can also be used. Forexample, adjusting screws can be used instead of racks.

[0027] The member 28 is arranged to cooperate with said powderdispensers for refilling of material. Further, the sweep of the member28 across the work surface is driven in a known manner through a servoengine (not shown), which displaces the member 28 along a guide rail 29,running along the powder bed.

[0028] At the laying down of a new powder layer, the thickness of thepowder layer will be governed by how far the worktable has been loweredin relation to the previous layer. This means that the thickness of thelayer may be varied as desired. Thus, it is possible to make the layersthinner when a cross section exhibits greater change in shape betweenadjacent layers, whereby a higher fineness of the surface is achieved,and to make layers equal to the maximum penetration depth of the beamwhen small or no changes in shape occurs.

[0029] In a preferred embodiment of the invention the ray gun 6 isconstituted by an electron gun, whereby the control members 7 for thebeam of the ray gun is constituted by deflection coils. The deflectioncoil generates a magnetic field that controls the beam generated by theelectron gun, whereby melting of the surface layer of the powder bed ina desired position is achieved. Further, ray guns comprise a highvoltage circuit 20, which is intended to supply, in a known manner, theray gun with an acceleration voltage for an emitter electrode 21,arranged at the ray gun. The emitter electrode is connected to a powersource 22 in a known manner, which source is utilised for heating theemitter electrode 21, whereby electrons are liberated. The function andcomposition of the ray gun are well known to those skilled in the art.

[0030] The deflection coil is controlled by the controlling computer 8,according to a laid-down running schedule for each layer to be fused,whereby control of the beam in accordance with the desired runningschedule may be achieved. A detailed description concerning thegeneration and correction of running schedules follows below, inconnection to the description of the drawing FIGS. 4-6.

[0031] Further, there is at least one focusing coil 7′, which isarranged to focus the beam onto the surface of the powder bed on theworktable.

[0032] The deflection coils and the focusing coils may be arrangedaccording to a multitude of alternatives well known to thoseknowledgeable in the art.

[0033] The apparatus is contained in a housing 15, which surrounds theray gun 6, and the powder bed 2. The casing comprises a first chamber23, surrounding the powder bed, and a second chamber 24, surrounding theray gun 6. The first chamber 23 and the second chamber 24 communicatesthrough a channel 25, which allows emitted electrons, which have beenaccelerated in the high voltage field of the second chamber, to proceedinto the first chamber, thereafter to impinge on the powder bed on thework table 2.

[0034] In a preferred embodiment, the first chamber is connected to avacuum pump 26, which lowers the pressure in the first chamber 23 to apressure of preferably about 10⁻³-10⁻⁵ mBar. The second chamber 24 ispreferably connected to a vacuum pump 27, which lowers the pressure inthe second chamber 24 to a pressure of about 10⁻⁴-10⁻⁶ mBar. In analternate embodiment, the first and second chambers may both beconnected to the same vacuum pump.

[0035] The controlling computer 8 is preferably further connected to theray gun 6, for regulating the emitted power of the ray gun, andconnected to the stepping motor 12 for adjustment of the verticalposition 2 of the work table between each consecutive laying down ofpowder layers, whereby the individual thickness of the powder layers maybe varied.

[0036] Further, the controlling computer is connected to said member 28for laying down powder on the work surface. This member is arranged inorder to sweep across the work surface, whereby a layer of powder islain down. The member 28 is driven by a servo engine (not shown), whichis controlled by said controlling computer 8. The controlling computercontrols the duration of the sweep, and secures that powder is refilledas needed. For this purpose, load indicators may be arranged in themember 28, whereby the controlling computer can be informed that themember is empty.

[0037] According to what is shown in FIG. 2, the device furthercomprises members 14 for sensing the surface characteristics of asurface layer at the powder bed. This member 14 for sensing thetemperature distribution of a surface layer at the powder bed 5 ispreferably constituted by a camera. In one preferred embodiment of theinvention, the camera is utilised partly for measuring the temperaturedistribution on the surface layer, and partly for measuring theoccurrence of surface irregularities through the shadow formation causedby irregularities on a surface. Information of the temperaturedistribution is used partly to achieve a temperature distribution assmooth as possible across the parts of the surface layer, which are tobe melted, and, partly, information may be used to control any deviationin measures between the generated three-dimensional product and theoriginal, since the temperature distribution reflects the shape of theproduct. In a preferred embodiment of the invention, the video camera ismounted on the outside of the casing 15 that contains the powder bed 5and the ray gun 6. In order to make the measurement of temperaturepossible, the casing is provided with a transparent window 16. Thepowder bed 5 is visible for the camera through this window. In apreferred embodiment of the invention, which is shown in FIG. 3, thewindow 16 is covered by a protective film 17. The protective film is fedfrom a feeder unit 18 to a collection unit 19, whereby the film issuccessively replaced, which has the effect that transparency can bemaintained. The protective film is necessary, since deposits arise as aconsequence of the melting process.

[0038] In FIG. 4, the procedure for generating primary running schedulesis shown schematically. In a first step 40 a 3D model is generated, forexample, in a CAD program, of the product to be manufactured,alternatively a pre-generated 3D model of the product to be manufacturedis fed to the controlling computer 8. Thereafter, a matrix is generatedin a second step 41, containing information of the appearance of crosssections of the product. In FIG. 7, a model of a hammer is shown,together with examples of thereto belonging cross sections 31-33. Thesecross sections are also shown in FIGS. 8a-8 c. The cross sections arelaid down in a density corresponding to the thickness of the separatelayers to be fused in order to make up the completed product.Advantageously, the thickness can be varied between the differentlayers. For example, it is advantageous to make the layers thinner inareas with a greater variation in the appearance of the cross sectionbetween adjacent layers. Thus, during the generation of the crosssections a matrix is created, which contains the information about theappearance of all cross sections, which together makes up thethree-dimensional product.

[0039] When the cross section has been generated in a third step 42, aprimary running schedule is generated for each cross section. Thegeneration of primary running schedules is based partly on recognitionof the shape of the parts that constitute a cross section, and partly onhow the running schedule affects the cooling temperature of local partsof a cross section. The object is to create a running schedule thatentails that the cooling temperature is as equal as possible in theparts that have been fused before the next layer is laid down, while atthe same time keeping the cooling temperature within a desired range inorder to reduce the risk for the occurrence of shrinkage strain in theproduct, and to reduce the magnitude of occurring shrinkage strain inthe product, leading to deformation of the product.

[0040] Primarily, a primary running schedule is generated, based on theshape of separate parts included in the cross section.

[0041] Thus, in a preferred embodiment of the invention, primary runningschedules are laid down, on the basis of experience of which runningschedules provides a good temperature distribution of the coolingtemperature of the-cross section, whereby the risk for shrinkage strainin the product, leading to deformation of the product, may be reduced.For this purpose, a set of running schedules for areas of differentshapes is stored in a memory. In a preferred embodiment, this memory isupdated during the course of evaluation of the results from correctingthe running schedule, whereby a self-educating system is obtained.

[0042] In an alternative embodiment of the invention, pre-formed crosssections, which have been generated by a separate computer, is fed to amemory in the controlling computer, where said primary running schedulesare generated. In this case, the information is obtained directly to thethird step 42, through an external source 40 a.

[0043] In FIG. 5, a procedure is shown schematically, in which the beamfrom the ray gun is controlled over the powder bed in order to generatea cross section of a product. In a first step 50, controlling of thebeam over the powder bed is initiated, according to the primary runningschedule defined in step 42. In the next step 51, the temperaturedistribution of the surface layer of the powder bed is measured by thecamera. Thereafter, a temperature distribution matrix, T_(ij-measured),is generated from the measured temperature distribution, in which thetemperature of small sub-areas of the surface layer of the powder bed isstored. When the matrix is generated, each temperature valueT_(ij)-measured in the matrix is compared the desired value in a matrixof desired values, T_(ij)-desired. Coarsely, the surface layer of thepowder bed may be divided into three categories. Firstly, areas in whichfusion is taking place through machining by the ray gun. In these areas,a maximum malting temperature T_(ij-max) is of interest. Secondly, areasalready fused, and which are thereby cooling. In these areas, a minimumallowed cooling temperature T_(ij-cooling-min) is of interest, since toolow a cooling temperature rives rise to tensions, and thereby to adeformation of the surface layer. Thirdly, areas not machined by the raygun. In these areas, the bed temperature, T_(ij-bed) is of interest. Itis also possible to compare the temperature only in machined areas,whereby T_(ij-bed) is not stored and/or controlled.

[0044] In a third step 52, it is tested whether T_(ij-measured) deviatesfrom the desired value T_(ij-desired), and whether the deviation exceedsallowed limits. The limits, ΔT_(ij-max), ΔT_(ij-cooling), andΔT_(ij-bed), belonging to the three different categories, are stored inthe controlling computer 8. It is also possible not to control the bedtemperature. In this case, the belonging limit value is not stored. In afourth step 53, it is investigated whether the machining of the surfacelayer is complete, provided that the deviation between T_(ij-measured)and T_(ij-desired) does not exceed this limit. If this is not the case,the run continues according to the effective running schedule, wherebythe abovementioned method steps 50-53 are run through one further time.If the deviation between T_(ij-measured) and T_(ij-desired) exceedseither of said limits, a correction of the running schedule 42 iscarried out in a fifth step. Said correction takes place in a preferredembodiment according to the scheme shown in FIG. 6. In a preferredembodiment of the invention, a new powder layer is not laid down untilthe completion of each layer, whereby the product is built throughsuccessive fusions until the product is completed. In this case, a newlayer is begun after a sixth step 55, provided that the product in itsentirety is not completed, when it is noted in the fourth step 53 thatthe running schedule for a layer is completed.

[0045] In a preferred embodiment, the running schedule comprises thefollowing method steps: In a first step 56, T_(ij-max) is compared toT_(ij-max)-desired. If T_(ij-max) deviates from T_(ij-max)-desiredexceeding ΔT_(ij-max), the energy supply to the powder layer iscalibrated in a step 56 a, either by changing the power of the beam, orby changing the sweep speed of the beam. In a first step 58,T_(ij-cooling) is compared to T_(ij-cooling)-desired. If T_(ij-cooling)deviates from T_(ij-cooling-desired) exceeding ΔT_(ij-cooling), therunning schedule for the beam is changed in a step 58 a. There areseveral ways to modify the running schedule for a beam. One way tomodify the running schedule is to allow the beam to reheat areas beforethey have cooled do much. The ray gun can then sweep across alreadyfused areas with a lower energy intensity and/or a higher sweep rate.

[0046] In a third step 60, it is investigated whether T_(ij-bed)deviates from T_(ij-bed-desired). If the deviation exceeds ΔT_(ij-bed),the temperature of the bed may in one embodiment of the invention becorrected in a step 60 a, for example, by making the beam sweep acrossthe bed for delivery of energy. It is also possible to attach equipmentfor separate heating of the bed to the device.

[0047] It is also possible that a control of the size of the object tobe manufactured takes place through the heat camera installed in thedevice. According to what has been described above, the bed, and theparts that have been fused, is measured. The recorded heat distributiontotally reflects the shape of the object in a section of thethree-dimensional body to be created. A control of the dimensions of theobject can thereby be carried out in a fourth step 62, and a feedback ofX-Y deflection of the beam of the ray gun may thereby be carried out. Ina preferred embodiment of the invention, this control is carried out ina step 62 a, in which the deviation between measures on the crosssection is determined, and, if the deviation is higher than allowed, theX-Y deflection of the ray gun is corrected.

[0048] Further, input signals from the camera may be utilised foridentifying the occurrence of surface irregularities, for example, inthe shape of a wielding spark. When the coordinates for surfaceirregularities have been identified, the running schedule may be updatedto the identified coordinate in order to melt the surface irregularity.

[0049] The invention is not limited to the embodiment described above;for example, the ray gun may be constituted by a laser, whereby thedeflection members are constituted by controllable mirrors and/orlenses.

[0050] The invention may be further utilised in a device for themanufacturing of a three-dimensional product through energy transferfrom an energy source to a product raw material, which device comprisesa work table on which said three-dimensional product is to be built, adispenser arranged to lay down a thin layer of product raw material onthe work table for the formation of a product bed, a member for givingoff energy to selected areas of the surface of the product bed, wherebya phase transition of the product raw material is allowed for theformation of a solid cross section within said area, and a controllingcomputer handling a memory in which information about successive crosssections of the three-dimensional product is stored, which crosssections constitute the three-dimensional product, where the controllingcomputer is intended to control said member for releasing energy so thatenergy is supplied to said selected areas, whereby saidthree-dimensional product is formed through successive bonding of crosssections, successively formed from powder layers laid down by the powderdispenser.

[0051] In this case, the embodiment is not limited to fusion of powdersthrough the radiation of the surface of a powder bed by a ray gun. Theproduct raw material may be constituted by any material that, after aphase transition, forms a solid body, for example, solidification aftermelting or curing. The energy-releasing member may be constituted by anelectron gun, a laser, controlled across the work surface, alternativelyby an energy-releasing member with the ability to project a crosssection directly on the product bed.

[0052] Otherwise, this embodiment may be equipped with all thecharacteristics, which are described in relation to the previouslydescribed embodiment.

1. A device for manufacturing a three-dimensional product, which devicecomprises a work table on which said three-dimensional product is to bebuilt, a powder dispenser which is arranged to lay down a thin layer ofpowder on the work table for the formation of a powder bed, a ray gunfor giving off energy to the powder whereby fusion of the powder takesplace, members for controlling the beam released by the ray gun acrosssaid powder bed for the formation of a cross section of saidthree-dimensional product through fusion of parts of said powder bed,and a controlling computer in which information about successive crosssections of the three-dimensional product is stored, which crosssections build the three-dimensional product, the controlling computerintended to control said members for guiding the ray gun across thepowder bed according to a running schedule forming a cross section ofsaid three-dimensional body, whereby said three-dimensional product isformed by successive fusion of successively formed cross sections frompowder layers successively laid down by the powder dispensercharacterised by that the device further comprises members for sensingsurface characteristics of a surface layer at the powder bed.
 2. Adevice according to claim 1, characterised in that said surfacecharacteristics is constituted by the temperature distribution of asurface layer at the powder bed.
 3. A device according to claim 1 or 2,characterised in that said surface characteristics is constituted by thesurface smoothness of a surface layer at the powder bed.
 4. A deviceaccording to any of claims 1-3, characterised in that said member forsensing of the temperature distribution is arranged to communicateinformation about the temperature distribution across the surface layerof the powder bed to said controlling computer, whereby said informationabout temperature distribution is intended to affect said runningschedule for the ray gun.
 5. Device according to claim 4, characterisedin that said information about the temperature distribution of thesurface layer of the powder bed is utilised to increase the energydelivery within areas of the surface layer of the powder bed with toolow temperature and decrease energy delivery within areas with too hightemperature whereby a more even working temperature of the crosssections is obtained.
 6. Device according to claim 4 or 5, characterisedin that said information about the temperature distribution is arrangedto control the energy delivery from the ray gun to the powder bed atfused areas within the presently uppermost powder layer, so that themaximum temperature after fusion at these areas is within a limitedrange.
 7. Device according to any of claims 4-6, characterised in thatsaid information about the temperature distribution is arranged tocontrol the energy delivery from the ray gun to the powder bed on theone hand fused at areas within the presently uppermost powder layer andon the other hand to be united with areas in a subsequent layer, so thatthe minimum temperature after fusion at these areas does not fall belowa predetermined limit.
 8. Device according to any of claims 4-6,characterised in that said information about the temperaturedistribution is arranged to control the energy delivery from the ray gunto the powder bed at areas on the one hand fused within the presentlyuppermost powder layer so that the minimum temperature after fusion atthese areas does not fall below a predetermined limit.
 9. A deviceaccording to any of claims 4-8, characterised in that said informationabout the temperature distribution is arranged to control the energydelivery from the ray gun to the powder bed at areas within theuppermost layer of the powder bed that are not so that the temperaturewithin these areas does not fall below a second predetermined limit. 10.A device according to any of claims 4-9, characterised in that saidinformation about the temperature distribution is arranged to be usedfor calibrating said member for controlling the ray gun.
 11. A deviceaccording to any of the preceding claims, characterised in that saidmember for sensing surface characteristics of a surface layer at thepowder bed is constituted by a camera.
 12. A device according to claim11, characterised in that the product bed is situated in a closedchamber, that the closed chamber exhibits a transparent window, and thatthe camera is arranged to record said surface characteristic of thepowder bed through this window.
 13. A device according to claim 12,characterised in that the transparent window is protected by a film,that said film is feedingly arranged along the window whereby new filmis fed whereby the transparency through the film and the window ismaintained.
 14. A device according to any of the preceding claims,characterised in that the ray gun is constituted by an electron gun, andthat the powder bed and the electron gun are enclosed within a vacuumchamber.
 15. Method for the manufacturing of three-dimensional bodiesthrough successive fusion of parts of a powder bed, which partscorrespond to successive cross sections of the three-dimensional body,which method comprises the following method steps: laying down a powderlayer on a work table, supplying energy from a ray gun according to apredetermined running schedule for the powder layer, fusion of the areaof the powder layer selected according to said running schedule for theformation of a cross section of said three-dimensional body, andformation of a three-dimensional body through successive fusion ofsuccessively formed cross sections from powder layers successively laiddown characterised in that the method further comprises sensing ofsurface characteristics of a surface layer situated at the powdered. 16.A method according to claim 15, characterised in that said sensedsurface characteristics comprise measuring of the surface smoothness ofa surface layer at the powder bed.
 17. A method according to claim 15 or16, characterised in that said sensed surface characteristics comprisemeasuring of the temperature distribution of a surface layer at thepowder bed.
 18. Method according to claim 17, characterised in that thesensed temperature distribution is utilised to calibrate the energysupply to the ray gun for the achievement of the correct meltingtemperature.
 19. A method according to any of claims 17 or 18,characterised in that the sensed temperature distribution is utilised toachieve a correct cooling temperature by modifying said runningschedule.
 20. A method according to claim 10, characterised in thatareas with a too low cooling temperature is reheated.
 21. A methodaccording to claims 19 or 20, characterised in that upon detection of anarea with a too high cooling temperature, the running schedule ismodified so that the build-up rate within this area is decreased.
 22. Amethod according to any of claims 17-21, characterised in that the bedtemperature is detected and that the bed is heated if the detectedtemperature falls below a predetermined limit.
 23. Method according toany of the claims 17-22, characterised in that the sensed temperaturedistribution is utilised to calibrate the members arranged at the raygun for the X-Y deflection of the beam.
 24. A method according to any ofclaims 16-23, characterised in that the following method steps are takenupon detecting a surface irregularity: the coordinates of the surfaceirregularity are registered and the beam generated by the ray gun isguided to said coordinates, where-after the surface irregularity ismelted.
 25. A device for the manufacturing of a three-dimensionalproduct through energy transfer from an energy source to a product rawmaterial, which device comprises a work table on which saidthree-dimensional product is to be built, a dispenser arranged to laydown a thin layer of product raw material on the work table for theformation of a product bed, a member for giving off energy to selectedareas of the surface of the product bed, whereby a phase transition ofthe product raw material is allowed for the formation of a solid crosssection within said area, and a controlling computer handling a memoryin which information about successive cross sections of thethree-dimensional product is stored, which cross sections constitute thethree-dimensional product, where the controlling computer is intended tocontrol said member for releasing energy so that energy is supplied tosaid selected areas, whereby said three-dimensional product is formedthrough successive bonding of cross sections, successively formed fromlayers of product raw materials laid down by the powder dispensercharacterised in that the device further comprises members for sensingof surface characteristics of a surface layer at the powder bed.
 26. Adevice according to claim 25, characterised in that said surfacecharacteristics is constituted by the temperature distribution of asurface layer at the product bed.
 27. A device according to claim 25 or26, characterised in that said surface characteristics is constituted bythe surface smoothness of a surface layer at the product bed.
 28. Adevice according to any of claims 25-27, characterised in that saidmember for sensing of the temperature distribution is arranged tocommunicate information about the temperature distribution across thesurface layer of the product bed to said controlling computer, wherebysaid controlling computer utilises this information for controlling saidmember for delivering energy to the product bed.
 29. A device accordingto claim 28, characterised in that said information about thetemperature distribution is arranged to be used for measurementcalibrating of said member for delivering energy to the product bed. 30.A device according to any of the claims 25-29, characterised in thatsaid member for sensing surface characteristics is constituted by acamera.
 31. A device according to claim 30, characterised in that theproduct bed is situated in a closed chamber, that the closed chamberexhibits a transparent window, and that the camera is arranged to recordsaid surface characteristic of the powder bed through this window.
 32. Adevice according to claim 31, characterised in that the transparentwindow is protected by a film, and that said film is feedingly arrangedalong the window whereby new film is fed whereby the transparencythrough the film and the window is maintained.